The testing of core-forming materials is an important part of foundry operations. Core breakage is a common phenomena in foundry practice, and the ability to compare the performance of various core sands and core sand-resin mixtures and to predict, in advance, core sand and core sand mixtures that will provide unacceptable performance is obviously beneficial. There are several test methods that are used to evaluate the ability of core sand and core sand mixtures to produce reliable cores. Several of the test methods used in the past to evaluate core-forming materials include the core tensile or dog bone method, the transverse disk, and the transverse load method in which cores 1″×1″×8″ (2.54 cm×2.54 cm×20.32 cm) are formed for testing. Such testing methods include testing of core strength, in which cores are made and broken in a transverse mode, core deflection, which is a measure of how much a core bends before breaking, which relates to core breakage attributed to core brittleness, core sand flowability, which evaluates the ease with which a prepared core-forming materials flow when blown into a core box, and core shrinkage, which relates to the ability of core sand mixtures to provide reliable casting dimensions.
The flowability of core sand mixtures is an important characteristic in the production of reliable cores. Core sand flowability is affected by a variety of variables, such as sand temperature, sand shape and size, resin percentage, and core additive types and amounts The ever-thinning core sections needed for modern castings make it especially important to determine the ease or difficulty with which a prepared core-forming material moves. How easily a prepared core sand mixture flows is important to good core formation, core density and strength. In the manufacturing of cores, prepared core sands must frequently flow downwardly, laterally, and then upwardly, to fill some small core area. An example of such requirements includes a water core jacket for an engine block head. The ability to determine in advance how well a core sand, core-sand-resin mixture, or other core-forming material will reliably produce a given core is important in choosing the right resin system or the right sand, or resin-sand mixture for use in production.
In the past, core sand flowability has been measured with a core box having a spiral core-forming passageway, and the flowability of core-forming materials in this system was measured by the distance core sand or core sand mixtures or other core-forming materials traveled down the spiral. While the results obtained with this prior core sand flowability test method were usable, a flowability testing method and apparatus that more closely represents what happens in actual production operations is desired.